AbstractA systematic investigation of the synthesis, physical properties, biodegradation, and drug release behavior of an aliphatic polynonanolactone from vegetable oil was performed. The chemical structure of the lactone monomers and polylactones were confirmed by NMR spectrometry and molecular weights were determined by gel permeation chromatography (GPC). The thermal behavior of the polymers was assessed by modulated differential scanning calorimetry (MDSC) and thermogravimetric analysis (TGA). The polynonanolactones are crystalline with melting enthalpies (ΔHm) ranging from 90 to 135 J/g. The crystalline nature of the polylactides was further evaluated by X‐ray diffraction (XRD) and peaks corresponding to planes (110), (200), and (210) were detected. The hydrolytic and enzymatic degradation properties of the polynonanolactones were studied and the degradation rate is comparable to that of widely used polycaprolactone. The enzyme proteinase K was used for the degradation of polynonanolactones. The extent of degradation was evaluated by scanning electron microscopy (SEM). Drug incorporation and release traits due to hydrolytic degradation of the polymer film was carried out with 5‐fluorouracil (5‐FU) as a model drug. This new class of polynonanolactones obtained from vegetable oil was demonstrated to be a potentially competent candidate to replace petroleum‐based polycaprolactone especially for drug delivery applications where slow release of drugs is a requisite. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6373–6387, 2009